Amplifier



5 Sheets-Sheet 1 AMPLIFIER c. w. HANSELL Filed Aug. 25, 1953 any 31,1938.

AA/ODE POM fl? .SIIPPZ Y 500/965 INVENTOR CZAAE/VCE Wf/AA/SELL ATTORNEYay 31, 1938. c. W. HANSELL 2,111,845

AMPLIFIER Filed Aug. 23, 1933 3 Sheets-Sheet 2 NQQER TU INVEVNTORLARENCE WJ/A/l/JZ'LL ATTORNEY C. W. HANSELL AMPLIFIER Filed Aug. 23,1933 3 Sheets-Sheet 3 INVENTOR L a J M H. w a m R M C n N m n A l'i'EThis invention relates STATES AMPLIFIER Clarence W. Hansell, PortJefierson, Y, as-

signor to Radio Corporation poration of Delaware Application August 23,

18 Claims.

to electron discharge device circuits, and particularly to such of thesecircuits as may be used for the amplification of signals.

An object of the present invention is to enable the amplification ofextremely wide bands of frequencies with simplicity and high efiiciency.

A further object is to provide an arrangement wherein there may beutilized vacuum tubes which function with high positive D. C. potentialson the control elements, but with little or no current fiow to thesecontrol elements.

These and other objects are achieved, in accordance with the presentinvention, by the provision of an axial magnetic field around anelectron discharge device whose output and input electrodes are suppliedpreferably with approximately equal positive potentials.

In one form of vacuum tube, which forms part of my invention, themagnetic field is arranged to have sufi'icient strength to reduce theanode current to zero while at the same time it permits considerablecurrent to flow to the grid. Under such conditions, if the anodepotential is varied the amount of grid current can also be variedwithout causing any flow of current to the anode which in this case mayact as the control element.

Since only a relatively small amount of anode power is needed for thispurpose the tube is thus available for power amplification.

One advantage of the present invention is that a magnetron may be usedfor the electron discharge device, or even an ordinary three elementtube which is supplied with an axial field.

Another advantage is that a system utilizing such electron dischargedevices in accordance with the present invention in a chain ofamplifiers avoids the necessity for employing blocking condensers orcoupling circuits between the anode of one tube and the controlelectrode of the next succeeding tube obtained a simplificationconsequently there is of the circuit and an increase in maximumoperating frequency without any difficulties due to capacity to ground,etc., of the blocking condensers or coupling circuits.

Referring to the drawings, Figure 1 shows a magnetron vacuum tube of atype which may anode magnetron tubes.

Figure 4 illustrates,

of America, a cor- 1933, Serial No. 686,338 (01. 179-171) in simplifiedform, the application of my invention to push-pull circuits and tocircuits in which undesired capacitive feed-back from output to inputcircuits is neutralized.

In Figure 1 there is illustrated in cross section 5 a magnetroncomprising an electron discharge device having an evacuated envelope l0containing within it at its center an electron emitting cathode IIsurrounded by an anode I2 and a grid-like structure l3. It is proposedto provide 10 this grid structure with rather widely spaced radial andvane-like elements on a circle almost as great as the diameter of theanode, as shown in the figure. This design, it has been found, gives theanode much more influence on the a0- 15 celeration of the electrons fromthe cathode, but still assures that nearly all the current will flow tothe grid. Externally of the envelope and surrounding it, is somesuitable means, such as a coil winding, for creating a magnetic field 20parallel with the cathode.

In the operation of this magnetron, both the grid structure I3 and theanode l2 are positively charged, as shown in Figure 2. When the cathodeII is maintained at a suitable incandescence by a heating current,electrons will, under ordinary circumstances, flow toward the grid l3and anode l2. When there is no magnetic field, the value of this currentis determined by various factors, among which are the impressed voltage,the 3 cathode temperature, the size and geometrical relations of theelectrodes, and the resistance of any output circuit which may beconnected to the electrodes. The electrons which carry or con stitutethis current travel outwardly in straight 35 radial paths from thecathode to the surrounding grid I3 and anode l2, and most of them willfall upon the anode. However, when a magnetic field is appliedsubstantially parallel to the cathode and hence substantially at rightangles to the 40 electric field between the electrodes, then theelectrons are deflected and caused to travel in a spiral path about thecathode on their way to the grid, as shown by dotted lines in Figure 1.As the field strength is increased, the fiow of cur- 4,5 rent to theanode ceases altogether for relatively weak fields because the vane-likeelements of the grid structure completely cut off the paths of theelectrons as the spiral paths of the electrons become longer; finally ata rather critical magnetic field strength, characteristic of anyparticular device, some of the electrons fail to reach the gridstructure 13 by reason of this deflection, thereby resulting in adecrease of grid current. When the field strength is still furtherincreased, above this critical value, the electron current rapidly fallsand is finally reduced substantially to zero. It is proposed in thepresent invention to adjust the value of the field strength so that theelectrons reach the grid structure only, while substantially no currentflows to the anode and it is under these circumstances that anyvariations in anode potential will vary the amount of grid currentwithout any flow of current to the anode. By means of these tubes onemay obtain a voltage amplification factor of 2 or 3 to one, or evenmore, depending upon the design of the tube and circuits.

Figure 2 shows an amplifier circuit using a chain of electron dischargedevices I, 2 and 3 in accordance with the present invention. Thesedevices may be either the magnetron illustrated in Figure 1 or anysuitable three element tube provided with coil windings, as shown. Thegrid or control electrode of each tube is shown connected to the anodeof the next succeeding tube, these electrodes both being supplied withequal positive potentials through impedances or resistances R from asource such as a generator, battery or rectifier.

In the operation of this circuit, variations in signal current receivedover an input circuit 5, which is illustrative of any desired receivingor transmitting arrangement, are applied to the anode of tube I, thuscausing variations in the amount of grid current without having any flowof current to the anode. Such variations in grid current of tube l inaccordance with the incoming signal waves cause a variation in voltagedrop (IR) to appear in impedance R in circuit with the grid, andconsequently a variation in the potential on the anode of electrondischarge device 2 which, in turn, influences the grid current flowingin the circuit of electron discharge device 2 similar to that heretoforedescribed, and so forth. The output circuit which is shown connected toelectron discharge device 3 and any suitable utilization circuit 6 willcontain fluctuations in current similar to those appearing in the inputcircuit 5, except that they have been amplified by each of thesucceeding tubes I, 2 and 3. If the vacuum tubes are properly designed,the output potential, current and power from the system may be made muchgreater than the input.

An arrangement as just described in connection with Figure 2 may be usedfor amplification of frequencies from about 20 to 1,000,000 cycles withhigh eficiency and should find a large field of usefulness in thetransmission of television signals.

Figure 3 shows a cascade resistance or impedance coupled amplifiersystem using split anode magnetron tubes 20, 2!, and 22. In this systemequal direct current potentials are preferably applied to the controland output anode elements of the same tube. The split anode magnetrontube, due to the curved paths taken. by electrons in the magnetic field,has the peculiar property of increasing the current flow to one anodewhen the potential of the other electrode is increased and vice versa.If I trace the paths of the electrons, it will thus be seen that withequal positive potentials on both anodes of the tube and with a criticalvalue of field, no electrons will flow to either anode element in theabsence of input signals, but that with an increase in the positivepotential to the control anode element due to a received signal,electrons will start to flow toward the control anode element but willreach only the output anode element on account of the radial paths ofthe electrons. Thus, fluctuations in potential applied to one anodecause fluctuations in the current flowing to the other anode. In Figure3, one anode of each tube is shown so connected that it serves as aninput electrode while the other anode serves as an output electrode.

Since the two anodes are usually identical in size and construction andsymmetrically located with respect to the cathode, it might, at firstthought, appear that no voltage gain can be obtained with the system.However, this is not the case since the interaction or regenerationeffect of the applied alternating current energy of the magnetron entersinto consideration and may cause a large voltage gain per tube. This maybe explained as follows: If the anode used as a control electrode hasits potential made more positive, the result is an increase in currentto the other electrode. Due to increased voltage drop in the series orcoupling impedance of the'other electrode, its potential is decreased.This, in turn, tends to reduce the current to the control electrode.Thus increased control grid potential results in decreased control gridcurrent, which is equivalent to regeneration or negative inputresistance. With associated circuits having insufficient loading due topositive resistance, this regeneration or negative resistance efiect canand does produce oscillation between the two electrodes at any frequencyto which the associated circuits are tuned. In the instant case, it maybe assumed that the negative resistance of the tube is balanced, toprevent oscillation, by the positive resistance of the couplingimpedances.

Referring to tube 2| in the diagram, let us assume that, due to theaction of the first tube, anode 23 has its potential increased. At oncethe current flow to electrode 24 is increased and this reduces thepotential of 24 by increasing the voltage drop in impedance Z". Butreducing the potential of 24 reduces the current flow to 23, raising-itspotential still higher, and so there is' effective regeneration withoutfrequency discrimination if the coupling impedances are resistances. Thepresence of regeneration is apparent from the fact that the split anodemagnetron, when adjusted for equal average current flow to bothelectrodes, is regenerative and capable of producing oscillations at anyfrequency to which the electrodes will respond. In other words, thesplit anode magnetron has a push-pull negative resistance. If thecoupling resistances are made to be equal to one another, or somewhatless than the efiective alternating current negative resistance, thenthere is obtained very great power amplification. By suitable circuitand tube adjustments the voltage, current and power gain per tube may bemade quite high and can approach infinity.

Figure 4 is similar to Figure 3 except that a push-pull arrangement isillustrated in which couplings between output and input circuits areneutralized, and more complex interstage coupling circuits are providedto widen the frequency response characteristic. Due to these extracomplications it is possible to obtain substantially equal amplificationfor all frequencies in an extremely large band from, say 0 to 2,500,000cycles. Of course, the type of tube illustrated in Figure 2, or anyother positive control grid type of tube may be used in this system.

Although there are shown circuits suitable for amplification ofrelatively low frequencies, it will be understood that my positivepotential control element system may also be used for radio frequencyamplification by substituting tuned circuits in place of the interstagecoupling impedances shown in the drawings.

I claim:

1. The combination with an electron discharge magnetron tube includingan electron emitting cathode, a grid surrounding said cathode, and acontrol electrode surrounding said grid, means for supplyingsubstantially equal positive direct current potentials to said grid andcontrol electrodes, and means for applying a magnetic field to saidelectrodes having a component at right angles to the electric fieldbetween said electrodes.

2. In combination, an electron discharge device including a cathode, acontrol and a controlled electrode, both said control and controlledelectrodes. extending along an appreciable portion of the effectivelength of said cathode, means for maintaining both control andcontrolled electrodes at positive potentials relative to said cathode.an input circuit coupled to said control electrode and cathode and anoutput circuit coupled to said controlled electrode and cathode, andmeans for applying a magnetic field to said electrodes of such a valuethat controllable electron current flows to the controlled electrode butsubstantially no electron current flows to the control electrode uponreceipt of signals from said input circuit.

3. An amplifier circuit comprising a vacuum tube having an imperforatecontrol electrode, a cathode, and a perforate controlled electrode, saidcontrol and controlled electrodes extending along an appreciable portionof the eiTective length of said cathode, means for maintaining saidcontrol and controlled electrodes at positive potentials with respect tosaid cathode, an input circuit coupled to said control electrode and anoutput circuit coupled to said controlled electrode.

4. A regenerative amplifier comprising a split anode magnetron having acathode and a pair of anodes extending along an appreciable portion ofthe effective length of said cathode, an input circuit connected to oneanode, and an output circuit connected to the other anode.

5. A cascade amplifier system comprising a plurality of split anodemagnetrons in series relation, each having a cathode and a plurality ofanodes extending along an appreciable portion of the effective length ofsaid cathode, an input circuit connected to one anode of each magnetron,and an output circuit connected to another anode of the same magnetron.

6. In combination, an electron discharge device comprising an envelopecontaining a control electrode, a grid, and a cathode, said controlelectrode and grid extending along an appreciable portion of theefiective length of said cathode, a magnetic field surrounding saidenvelope, means to apply approximately equal high positive potentials toboth said control electrode and grid, an input circuit coupled to saidcontrol electrode, and an output circuit coupled to said grid.

'7. In combination, an electron discharge device amplifier comprising anenvelope containing a control electrode, a grid, and a cathode, saidcontrol electrode and grid extending along an appreciable portion of theeffective length of said cathode, means to apply approximately equalhigh positive potentials to both said control electrode and grid, amagnetic field parallel to said cathode whereby current to said controlelectrode is reduced to zero and current flows to the grid, means tovary the positive potential on said control electrode in accordance withthe signal to be amplified, and utilization means coupled to said grid.

8. An amplifier having, in combination, a first electron dischargedevice comprising a control electrode, cathode and grid, said controlelectrode and grid extending along an appreciable portion of theefiective length of said cathode, and a magnetic field surrounding saidelectrodes, a second electron discharge device similarly arranged, adirect wire connection between the grid of said first device and thecontrol electrode of said second device, means for supplying overseparate paths a positive potential to said wire connection and to thecontrol electrode of the first device and to the grid of said seconddevice, an input circuit connected to the control electrode of saidfirst device and an output circuit coupled to the grid of said seconddevice.

9. A regenerative amplifier comprising a split anode magnetron having acathode and a pair of anodes oppositely disposed with respect to andextending along an appreciable portion of the effective length of saidcathode, an input circuit connected to one anode and an output circuitconnected to the other anode, and means for applying positive potentialsto both of said anodes.

10. In combination, an electron discharge de vice having a cathode, agrid electrode surrounding said cathode, and a control electrodesurrounding said grid, means for supplying positive potentials to saidgrid and control electrodes with respect to said cathode, an inputcircuit coupled to said control electrode, and an output circuit coupledto said grid electrode.

11. In combination, an electron discharge device having a cathode, agrid electrode surrounding said cathode, and a control electrodesurrounding said grid, means for supplying positive potentials to saidgrid and control electrodes with respect to said cathode, means forapplying a magnetic field parallel to said cathode, an input circuitcoupled to said control electrode, and an output circuit coupled to saidgrid.

12. In combination, an electron discharge device comprising an evacuatedenvelope having within it a pair of anodes oppositely disposed withrespect to a central cathode located between said anodes, a coilsurrounding said envelope for applying a magnetic field parallel to saidcathode, an input circuit coupled to one of said anodes, and an outputcircuit coupled to the other of said anodes.

13. In combination, an electron discharge device comprising an evacuatedenvelope having within it a pair of anodes oppositely disposed.

with respect to a central cathode located between said anodes, a coilsurrounding said envelope for applying a. magnetic field parallel tosaid cathode, means for applying positive potentials to both saidanodes, an input circuit coupled to one of said anodes, and an outputcircuit coupled to the other of said anodes.

14. In combination, an electron discharge device comprising an evacuatedenvelope having within it a control anode and a controlled anodeoppositely disposed with respect to a central cathode located betweensaid anodes, a coil surrounding said envelope for applying a magneticfield parallel to said cathode, a second similar electron dischargedevice, a neutralization circuit coupling the control anode of eachdevice with the controlled anode of the associated device, a connectionbetween the cathodes of both devices, means for applying positivepotentials to the control anodes of both devices, an input circuitconnected to the control anodes of both devices, and a utilizationcircuit coupled to the controlled anodes of both devices.

15. In combination, an electron discharge device comprising an evacuatedenvelope having within it a control anode and a controlled anodeoppositely disposed with respect to a central cathode located betweensaid anodes, a coil surrounding said envelope for applying a magneticfield parallel to said cathode, a second similar electron dischargedevice, a neutralization circuit coupling the control anode of eachdevice with the controlled anode of the associated device, a connectionbetween the cathodes of both devices, means for applying positivepotentials to the control and controlled anodes of both devices, aninput circuit coupled to the control anodes of said devices, and autilization circuit coupled to the controlled anode of said devices.

16. The method of operating an electron discharge device having acathode, a control and a controlled electrode, both extending along anappreciable portion of the effective length of said cathode, whichcomprises maintaining both said control and controlled electrodes atsubstantially equal positive potentials with respect to said cathode andapplying a magnetic field to said device parallel to said cathode ofsuch a value that an increase in positive potential to said controlelectrode will cause electrons emanating from said cathode to impingesolely on said controlled electrode.

17. In combination, an electron discharge device including a cathode, acontrol and a controlled electrode each in the form of a cylindersurrounding said cathode for an appreciable portion of the effectivelength thereof, said controlled electrode being perforated and locatedintermediate said cathode and control electrode, means for maintainingboth control and controlled electrodes at positive potentials relativeto said cathode, an input circuit coupled between said control electrodeand cathode, an output circuit coupled between said controlled electrodeand cathode, and means for applying a magnetic field to said electrodesof such a value that controllable electron current flows to thecontrolled electrode but substantially no electron current flows to thecontrol electrode upon receipt of signals from said input circuit.

18. An amplifier system having, in combination, first and secondelectron discharge devices each having a cathode, a grid surroundingsaid cathode and an anode surrounding said grid, a coil surrounding eachdevice for producing a magnetic field in a direction parallel to theoathode thereof, a source of signals coupled to the anode of said firstdevice, a direct connection between the grid of said first device andthe anode of said second device, an output circuit coupled to the gridof said second device, and means for applying direct current potentialsto said anodes and grids which are positive with respect to theirassociated cathodes.

CLARENCE; W. HANSELL.

